Mechanical instruments for measuring and displaying process variables, such as pressure or temperature, are widely used throughout the industry. These instruments typically do not require any source of electrical power and display their respective process variable using mechanical techniques. For example, a Bourdon tube device generates movement of a needle in direct response to a pressure change within a Bourdon tube that is exposed to a pressure. Similarly, a temperature measurement device may have a needle that is coupled to a bimetallic strip that is sensitive to changes in temperature. These are simply two examples of ubiquitous mechanical devices that continue to exist in process installations today. By virtue of their mechanical nature, these devices are not affected by power failure and are also relatively inexpensive to produce and deploy.
As the cost of microelectronic components has dropped in recent years, there is now the ability to compete on a cost basis with the mechanical process variable measurement and display devices listed above. However, the industry is generally aware of the abilities and prices of mechanical devices. Thus, as new devices that employ electronic components attempt to compete, they must generally provide additional features at similar or less cost. One way in which such electronic devices have done this is by mimicking the overall display of a mechanical transducing device. For example, a self-powered optical detector for mechanical gauge instruments is provided in US Patent Application Publication Number 20140239151 A1. This device while employing some electronic components, generally mimics the appearance of a Bourdon tube gage.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.